In general, young children with the 22q11.2 deletion syndrome have delays in motor milestones (mean age at walking of 18 months), delay in emergence of language (many are nonverbal at age 2-3 years), and autism/autistic spectrum disorders in approximately 20% [Fine et al 2005].
Specifically, in a study of 28 toddlers assessed with standardized tests, mental development was average in 21%, mildly delayed in 32%, and significantly delayed in 46%; in motor development, 8% were average, 13% were mildly delayed, and 79% were significantly delayed.
In a group of 12 preschoolers assessed using the WPPSI-R, the full-scale IQ was 78±11, the mean performance IQ was 78±14, and the mean verbal IQ was 82±15. In total language, 16% were average, 44% were mildly delayed, and 40% were significantly delayed [Solot et al 1998].
Older individuals with 22q11.2 deletion syndrome generally have an atypical neuropsychologic profile across multiple domains, the most striking aspect of which is a significantly higher verbal IQ score than performance IQ score. Moss et al  observed a mean split between the verbal IQ and performance IQ in 66% of 80 school-age children consistent with a nonverbal learning disability that is rare in the general population [Wang et al 1998]. Because the full-scale IQ score alone does not accurately represent the abilities of many individuals with 22q11.2 deletion syndrome, verbal and performance IQ scores need to be considered separately. In addition, affected individuals exhibit relative strengths in the areas of rote verbal learning and memory, reading decoding, and spelling. Deficits are found in the areas of nonverbal processing, visual-spatial skills, complex verbal memory, attention, working memory, visual-spatial memory, and mathematics. This evidence of stronger verbal than visual memory skills and stronger reading than math skills also supports the presence of a nonverbal learning disorder that requires specific cognitive remediation, behavior management, and parental counseling.
In a group of 80 school-aged children assessed with the age-appropriate Weschler IQ test, the mean IQ score was 76, whereas, 18% attained full-scale IQ scores in the average range, 20% in the low-average range, 32% in the borderline range, and 30% in the retarded range.